Trick for starting with a dead 12 volt battery?

What I think happens is unlike pushing the Start button with the brake pedal pressed, using the AC remote button doesn't use as much power before the HV contactor closes since it doesn't turn on the dash, the (daylight) running lights, the seat heaters (if turned on), the inside lights, the brake lights (brake pedal pressed when pressing the Start button). Hybrid Assistant also can't get the full data from the car so maybe not all ECU are running. All these are running of the 12V battery.

 

This is exactly how it works. Regenerative charging is when the car coasts in either D or B, or the brakes are applied; the foot brake is regen under light foot pressure, then part regen & part friction braking with greater foot pressure.

 

It is supposed to work that way. Non-plugins can reach 100% very quickly.

 

Don't forget the brake booster-accumulator, which can be a major power hog for a brief time when the brake pedal is first pressed, or even just opening the driver door. Avoiding that might help out a weak 12V battery on the cusp of failure.

 

If the 12v is completely dead, you can't even open the lift gate from the outside to get to it. I just had this problem with my 2014 Prius Three (not a prime). Below 0 temps and the battery died. The hookup under the hood to charge it didn't seem to be working (or more likely I was too impatient), so I had to climb in through the seats, open the inside cover and pull the latch. Not too easy for an Old man who recently had my hip replaced! I also had to use the metal key to open the driver door - No battery no door locks!

Moral of the story - replace your battery at 5 years or at least have it thoroughly tested. When it gets really cold it's too late and makes it even more difficult and uncomfortable to replace it!

 

Beginning with Gen 4 in 2016, they moved the 12V battery to the engine bay, so accessing without any power is no longer a problem. Also charging/jumping is easier due to the terminals being available there also.

 

But the Gen 5 put the battery right back in the trunk, although they do have terminals under the hood to boost.

 

Gens 2 and 3 had jump/charge terminals under the hood also, with the battery in the back. I guess the point is Toyota won't let you get "locked out" of access to your battery terminals from a dead battery no matter where the physical battery is.